Abstract
We examine the phylogenetic structure and morphological differentiation within the Hynobius kimurae–H. boulengeri species complex—a widely-distributed group of stream-breeding hynobiid salamanders, inhabiting montane areas of western, central and eastern parts of Honshu Island, Japan. Phylogenetic relationships were assessed based on analyses of mitochondrial (mtDNA) and nuclear (nuDNA) gene fragments for a total of 51 samples representing 23 localities covering the entire range of the species complex. Morphological study included one-way analysis of variance (ANOVA) and principal components analysis (PCA) analyses of 26 morphometric and six meristic characters for 38 adult specimens of H. kimurae and three adult specimens of H. boulengeri. MtDNA genealogy supported monophyly of the H. kimurae–H. boulengeri complex, which is sister to all other Hynobius except H. retardatus. The complex is subdivided into three major clades, corresponding to the Eastern (Clade I) and Western (Clade II) populations of H. kimurae sensu lato, and to H. boulengeri (Clade III). Monophyly of H. kimurae sensu lato is only moderately supported by mtDNA, while nuDNA suggested that the Western form of H. kimurae is closer to H. boulengeri than to the eastern form. The time of the split of the H. kimurae–H. boulengeri complex is estimated as late Miocene and coincides with intensive crust movement in western Japan. Divergence between Clades I and II took place in early Pliocene and was likely influenced by the uplift of Central Japanese Highlands. All three clades were found to be different in a number of morphological characters, allowing us to describe the eastern form of H. kimurae as a new species, Hynobius fossigenus sp. nov.
Highlights
Stream-dwelling freshwater organisms are promising models for studies of the interdependence between geological history and formation of biota
Under the general lineage concept (GLC) we follow the framework of integrative taxonomy (Padial et al, 2010; Vences et al, 2013) that combines multiple independent lines of evidence to assess the taxonomic status of the lineages in question: mtDNA-based molecular genealogies were used to infer species boundaries, univariate (ANOVA) and multivariate (PCA) morphological analyses were used to describe those boundaries, while nuDNA-marker was analyzed to test the concordance between phylogenetic signals from mtDNA-based genealogy and nuDNA-based phylogeny
Our study clarified the phylogeographic pattern of the H. kimurae– H. boulengeri species complex and documented the presence of a new species—Hynobius fossigenus sp. nov., inhabiting central Honshu
Summary
Stream-dwelling freshwater organisms are promising models for studies of the interdependence between geological history and formation of biota. Due to their limited dispersal abilities salamanders are readily isolated by geographical barriers such as mountains, river valleys and sea straits (Avise, 2000; Tominaga et al, 2006; Poyarkov et al, 2012). A number of seminal works on freshwater fish, for example, demonstrated significant structuring within wide-ranged species complexes distributed across Honshu Island of Japan that suggest the presence of cryptic lineages in the northeastern and southwestern parts of the island (Machida et al, 2006; Watanabe et al, 2006; Tominaga, Nakajima & Watanabe, 2016). These lineages are often separated by Fossa Magna: the tectonic fault zone crossing the center of what currently is the Honshu Island, which divided the southwestern and northeastern paleo-Japanese landmasses in the past (Kato, 1992)
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